Five-bar compressor

ABSTRACT

The invention is a 180° reciprocating piston compressor comprising additional eccentric disc linkage between the crankpin and the connecting rod. The additional linkage lessens the compression above the piston during start-up and limits the electrical motor shaft load at design operating conditions lowering the starting current surge when bringing the system up to starting speeds. The additional disc eccentric linkage also lessens the torque load on the motor during motor normal operating speed.

CROSS REFERENCES

The present invention is based in part on U.S. Pat. No. 4,319,498 Mar. 16, 1982 and U.S. Pat. No. 4,467,756 Aug. 28, 1984. Presenting new and useful improvements in continuing development of electrical motor driven compressors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to electrical motor driven reciprocating piston compressors. The system is also applicable to engine driven systems.

2. Description of Prior Art

The primary object of the novel mechanism presented in the Cross References was directed toward the design of reciprocating piston internal combustion engines as indicated and described in their respective Summaries. In the present invention the characteristic 5-bar linkage is employed for use in small efficient electrical motor driven domestic air conditioning and refrigeration systems. The linkage presented is also adaptable to larger commercial systems requiring additional speed control using centrifugal switches on heavier starter windings and motor shaft mechanical governors.

The primary objective of the present application is directed toward lowering urban electrical grid load during peak summer temperatures which result from the necessary area wide use of additional air conditioning and extended use of refrigeration equipment. In the present invention this is accomplished by limiting surge electrical current during high torque start-up loads by decreasing the compressor initial piston loads and cylinder swept-volume. This is accomplished by limiting the distance of the piston stroke in its upward travel in the compressor cylinder to top-dead-center (TDC) during the initial crank acceleration at start-up when the inertia of reciprocating components is low.

The invention also lowers steady-state current flow in the compressor motor during periods of full-load torque and full speed at rated frequency and voltage by decoupling piston maximum pressure loads from the motor shaft by allowing the compressor piston and connecting rod to float free from the crankpin at its upward stroke position of 270° when its acceleration is highest allowing it to proceed under its own inertia to complete the full stroke at TDC. The ability to decouple the maximum compressor piston loads from the electric motor shaft prevents breakdown-to-torque overload exceeding rated voltage resulting in loss of motor speed and over heating during periods of urban heavy electrical grid load preventing motor damage.

Previous disclosures described in Cross-References 1 and 2 reduced first harmonic induced vibration by the use of crankpin cheek counterbalances. Cheek counterbalances are not used in the present invention which employs an opposed cylinder arrangement using a two-throw crankshaft with 180° between cranks of opposing cylinders. This arrangement provides full static balance and lightens crankshaft weight lessening starting torque and current surge and these become novel features of the new and useful improvements enhancing the design.

SUMMARY OF THE INVENTION

The primary object of the invention is the design of a small efficient electric motor driven compressor for domestic use in air conditioning and refrigeration equipment.

It is another object of the invention to increase the scope of the design to enable its usage in larger scale commercial future applications by heavier centrifugal switches on starter windings and the use of mechanical governors.

Another important object of the invention is to lessen the vibration of the reciprocating piston system of the general character described in the Cross References by simultaneously sequencing and distributing the said reciprocating loads upon each side of the crankshaft within a 180° opposed cylinder arrangement.

It is yet another object of the invention to eliminate the incidence of electrical motor damage during periods of high urban grid power usage and loss of power when the motor overheats at rated voltage at lower speed.

A further object of the invention is to construct a piston compressor having a plurality of 180° opposed crank throws.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a 180° opposed two-throw crankshaft.

FIG. 2 is a frontal view of a crank eccentric disc.

FIG. 3 is a frontal view of the said crank eccentric disc of FIG. 2 assembled within the compressor connecting rod.

FIG. 4 is a side view of the connecting rod assembly of FIG. 3.

FIG. 5 is a top view of the compressor reciprocating components rotatively mounted within a compressor crankcase, said crankcase shown in cross-section, cylinders and upper head components, also shown in cross-section, mounted on said crankcase. The larger journal of the connecting rod of FIG. 4 is shown rotatively mounted on the crankpins of the two-throw crankshaft of FIG. 1, said connecting rod piston pin boss pivotally mounted in a piston shown in cross-section, said piston being slidably mounted in said cylinder.

FIG. 6 is a series of front views of the reciprocating components of the compressor comprising the crankshaft of FIG. 1, the eccentric disc of FIG. 2 and the connecting rod of FIG. 3 as they are positioned relative to axial center of the compressor cylinder bore at crank angular positions of 0° (BDC), 270°, 360° (TDC) and 90° of crank rotation at compressor normal operating speed when piston rectilinear inertial and pressure loads are acting on the compressor piston at set design conditions.

FIG. 7 is a top view of a four-throw 180° horizontally opposed crankshaft comprising the same elements of the 180° horizontally two-throw crankshaft of FIG. 1 with elements arranged in the same horizontal plane and having additional main shaft support.

FIG. 8 is a top view of a pair of 180° opposed two-throw crankshafts in which each opposed set of crank-throws are perpendicularly aligned to each other about the main shaft center of rotation at 90° intervals.

DETAILED DESCRIPTION OF THE INVENTION

The invention is a 180° horizontally opposed cylinder compressor. The novelty of the invention is an eccentric disc rotatively mounted between the compressor connecting rod and crankpin which synergistically react under system inertial rotative loading, rotate on each of the crankpins of the crankshaft of FIG. 1 and thereby coordinates the variability of positions of said pistons slidably mounted in said 180° opposed cylinder arrangement. The eccentricity of the said eccentric discs act as an additional linkage or fifth bar and this linkage when its rotation is partially constrained adding an additional degree of freedom to determinate piston motion and position when calculated from the inertial mass of reciprocating components and fluid pressures above the piston at a given crankshaft rotational position and speed. Balancing reciprocating inertial loads and pressure loads above the piston, independent of the electrical motor shaft torque, decreases the starting and nominal motor loads and subsequently lowers current flow to said motor armature and field windings improving motor efficiency.

FIG. 1 is a top view of a 180° two-throw crankshaft comprising main shaft 11 crank arm 2, crankpin 3, constraining pin 4, second crank arm 5, and second constraining pin 7. The crankshaft shown in FIG. 1 is used in a horizontally opposed two cylinder compressor. The number of paired crank elements shown are not limited to operation with only two cylinders but may be increased in number to operate with a plurality of opposed cylinders in an inline arrangement, or aligned radially about the center of crank rotation.

The fixed crank radius (r) of the crankshaft shown in FIG. 1 is the distance between the axial center line of main shaft 1 and the axial center line of crankpin 3 and likewise about the opposed axial center line of crankpin 6. The said fixed crank radius (r) is variably augmented by the eccentricity (e) of eccentric disc 8 shown in FIG. 2.

FIG. 2 is a front view of eccentric disc 8 that is rotatively mounted in connecting rod 13 shown in FIG. 3. Featured elements of eccentric disc 8 shown in FIG. 2 are crankpin bore 9, and crankpin bore axial center 12. The distance between the axial center 12 of crankpin bore hole 9 and the axial center 11 of eccentric disc 8 is the eccentricity (e) of eccentric disc 8. Pivotal rotation of eccentric disc 8 on crankpin 3 and likewise on crankpin 6 variably augment the said fixed crank radius (r) such that (r+e) become the effective full swing crank radius which varies through out rotation during operation.

FIG. 3 is a front view of eccentric disc 8 rotatively mounted in bearing 14 that is fixedly held in connecting rod 13 journal 15 at the opposite end of connecting rod 13 is piston pin boss 16 for pivotally mounting a piston.

FIG. 4 is a side-view of connecting rod 13 and this view is also shown in two places in the compressor assembly drawing of FIG. 5.

FIG. 5 is a top view of a horizontally opposed two cylinder compressor shown partially in cross-section. Rotatively mounted in the compressor crankcase 18 is main shaft 1 of the 180° opposed two-throw crankshaft shown in FIG. 1. Eccentric discs 8 are rotatively mounted in connecting rod journals 15 which are in turn rotatively mounted on crankpin 3 and crankpin 6. At the opposite end of connecting rod 13 the piston pin boss 16 is pivotally mounted in piston 20 shown in cross-section slidably mounted in cylinders 19 also shown in cross-section. Clamped between cylinder 19 and head 23 is valve plate 22 comprising a reed valve clamped by cleat and screw to control flow in the discharge circuit 28 and a lower reed valve pinned between cylinder head 23 and cylinder 19 to control inlet circuit 29. The novelty of the invention is seen in the 180° opposed layout of the compressor cylinders in which the lateral forces of the accelerated compression stroke of the free floating connecting rods 13 and pistons 20 providing counter balance of opposing active forces reducing the compressor vibration.

Turning now to FIG. 6 which describes the four primary cyclic events occurring during rotation of main shaft 1 of the horizontally opposed two-throw crankshaft of FIG. 1. The reciprocating events occurring in the right hand cylinder 20 are the same as those occurring in the opposite left hand cylinder 20 and the dynamic loads occurring in each cylinder are equal and opposed.

FIG. 6 a shows the relative position of connecting rod 13 at bottom-dead-center as it is vertically aligned with crankpin 6 and constraining pin 7. The rotative axis of main shaft 1 (not visible) is also directly aligned above crankpin 6. In this configuration the eccentricity (e) of disc 8 is aligned with the fixed crank radius (r) and thus the apparent crank radius effecting piston 20 position in cylinder 19 of FIG. 5 is the sum of (e+r) and this results in a lower piston position during the induction stroke a design circumstance which enhances the compressor volumetric efficiency.

FIG. 6 b shows the relative position of the reciprocating components when crank arm 5 is at the 270° position of its upward swing. Again the fixed crank radius (r) and the eccentricity (e) are aligned and additive and working together they shift the mass of the lower connecting rod elements and disc 8 further to the left. Piston speed is accelerated to the highest degree at the 270° crank position and can be shown to be 1.57 times the average piston velocity. Because of the higher mass (m), at the extended radius (e+r) and because of the highest velocity at the 270° crank position the force (F=ma) is highest during the compression stroke and is used to accelerate the piston upward against the higher developing piston pressures. Approaching the 270° position the vertical travel of the crankpin begins to slow causing the inertial loads to carry the piston upward and constraining pin 7 and 4 to change positions in constraining slot 10, pivot concentrically about crankpin 6 allowing piston 20 to float upward against the piston pressure load and thus decouples the main shaft 1 load from the electrical motor shaft load as the crank rotation approaches TDC. The upward deceleration of constraining pin 7 at the 270° position of crank rotation causes constraining pin 7 to change its position in constraining slot 10 by the inertial rotation of eccentric disc 8 concentrically about crankpin 6 while the faster upward rectilinear motion of piston 20, shown in FIG. 5, and connecting rod 13 inertial load also cause eccentric disc 8 to rotate in journal 15 of connecting rod 13 and allow piston 20 to float upward for a distance (s) during compression. This inertial vertical impulse measured in pounds (lb) over the distance (s) where (s=e) is the amount of work produced in foot-pounds for a given reciprocating mass (m) given by F=ma and equated in foot-pounds.

At crank TDC as shown in FIG. 6 c it is once again seen that the fixed crank radius and eccentricity (e) are vertically aligned thus increasing the effective crank arm radius. At this point the clockwise rotation of crank arm 5 and the lower induction pressures above the piston causes the constraining pin 7 to move downward in constraining slot 10 and contact the other end of the constraining slot 10 as it approaches the 90° clockwise rotational position during the intake stroke.

FIG. 6 d shows the reciprocating components at the 90° position of crank rotation with constraining pin 7 now at the other end of constraining slot 10. Where it remains until crankpin 6 once more rotates to the 270° position of crankshaft rotation imparting high speed inertia loads to the upward movement of connecting rod 13 and piston 20 allowing piston 20 to float free in the last half of the upward compression stroke and thus decouples the compressor compressive torque load from main shaft 1 load and thereby lower the power requirement of the electric motor.

FIG. 7 is a four-throw crankshaft comprising a pair of 180° horizontally opposed two-throw cranks similar to that shown in FIG. 1 and having the same numbered elements of FIG. 1. Each set of the pair of two-throw cranks are joined in-line across a supporting main journal 26. The second set of the 180° opposed two-throw crankshafts is supported during rotation by assembly main aft shaft 27.

FIG. 8 is a four-throw crankshaft comprising a pair of 180° opposed two-throw crankshafts. Each set of the pair are aligned at 90° to main shaft rotation. Although the crankshaft of FIG. 8 has a different alignment of throws aligned on each side of main shaft 1, the numbered elements are the same. Constraining pin 4 is not seen in FIG. 8 because it is below crankpin 3.

NUMBERED ELEMENTS

-   1. main-shaft -   2. crank-arm -   3. crankpin -   4. constraining pin -   5. center crank-arm -   6. crankpin -   7. constraining pin -   8. eccentric disc -   9. crankpin bore hole -   10. constraining slot -   11. disc axial center -   12. crank bore axial center -   13. connecting rod -   14. bearing -   15. connecting rod journal -   16. piston pin boss -   17. piston pin -   18. crankcase -   19. cylinders -   20. pistons -   21. cylinder head -   22. valve plate -   23. head -   24. -   25. cylinder bore centerline -   26. main shaft -   27. main aft shaft -   28. discharge circuit -   29. inlet circuit 

1. An opposed two cylinder compressor having a 180° opposed two-throw crankshaft rotatively mounted in a crankcase, said crankshaft comprising a main shaft, two aligned crank arms fixedly attached to a crankpin, a second crankpin fixedly attached to the outer surface of one crank arm forming a second crank throw, said main shaft fixedly attached to the outer surface of the other crank arm, said crankpins and said main shaft axial centers are in parallel alignment, adjacent and below each of the said crankpins a constraining pin fixedly mounted on the said crank arms, eccentric discs having a constraining slot in which the said constraining pins are slidably mounted, said eccentric discs having a crankpin bore hole for rotatively mounting on said crankpins, said eccentric discs rotatively mounted on one end of a connecting rod, said connecting rod rotatively mounted on each of the said crankpins, the other end of each of the two said connecting rods pivotally mounted within pistons, each said piston slidably mounted in said opposed cylinders, said cylinders closed at one end by a head, a valve plate positioned between each said cylinder and each said head.
 2. The compressor of claim 1 having four opposed cylinders positioned in-line on the same horizontal plane, a second 180° opposed two-throw crankshaft fixedly attached to the said crankshaft of claim 1 by a mainshaft, said second crankshaft, having an aft main journal.
 3. The compressor of claim 1 having four cylinders, said four cylinders arranged in two sets of opposed cylinders in which the opposing lines are perpendicular, said perpendicular arrangement positions each cylinder in 90° quadrants about the axial center of crankshaft rotation. 